1. Field of the Invention
This invention relates to a centralizing device for an elongated body in a mousehole machine. More particularly, it relates to a centralizing device which is arranged in a mousehole machine to centre an elongated body which is in the mousehole machine, the centralizing device being at the upper portion of the mousehole machine. The centralizing device is supported and rotatable on a mainly horizontal axis of rotation extending through the opening of the mousehole machine, the centralizing device comprising centralizing bows located on opposite sides of the axis of rotation.
2. Description of Related Art
All indications of direction, such as horizontal and vertical, refer to the equipment arranged in the working position. The work of building a pipe string from pipes and running the pipe string into a borehole or a well and the work of pulling a pipe string out of a borehole or a well and breaking out the pipes of the pipe string are mainly carried out from a drill floor. At their end portions the pipes are provided with threads, and the pipes are connected and disconnected by screwing. Screwing operations are performed by means of motor-driven tools.
The work process is made more efficient by moving some screwing operations and handling of single pipes out of the central area on the drill floor, that is, away from the centre of the borehole or well.
This is achieved by first joining, outside the central assembly area, a few pipes, for example three or four pipes, into a pipe string section which, in turn, is carried to the central assembly area to be included in the pipe string, possibly via an intermediate storage. Correspondingly, a pipe string is disassembled by first being divided into pipe string sections, each consisting of several pipes. Each pipe string section is carried away from the central assembly area for further disassembling. The screwing operations are thereby divided between two assembly areas on the drill floor, a central assembly area near the centre of the borehole or well, and a non-central assembly area.
It is common to place pipes and pipe string sections in a so-called mousehole, here called a mousehole machine, in the drill floor in connection with screwing operations taking place outside the central area.
A mousehole machine comprises a substantially vertical, tubular sleeve which is open at its upper end and which is provided with a pipe support below the upper end portion of the sleeve, for example in the form of a possibly movable end plate-/bottom plate at the lower end portion of the sleeve. The mousehole machine is installed below the drill floor and concentrically to an opening, a hole, in the drill floor. The depth of the mousehole machine is determined by the location of the pipe support.
During make-up and break-out of the pipes it is important that the pipe which is in the mousehole machine is centred in the mousehole machine to engage in the mechanized pipe tongs used. The prior art includes the use of leaf springs which are installed in the mousehole machine to centre the pipe. Further it is known to use elastic packers or bushings of adapted dimensions. It is also known to use hydraulic or mechanical centralizing devices, typically including three plates distributed around the central axis of the mousehole machine, which are arranged to be moved radially towards the central axis to centre the pipe.
Prior art devices are either complicated, and thereby relatively costly to buy and operate, inaccurate or cumbersome in use.